FINAL neuro Flashcards
What is CN IV (name, sensory vs. motor function)
Trochlear, motor
Function of CN IV
Superior oblique muscle of the eye
How is CN IV tested?
With CNIII- tracking moving objects
What is CN V (name, sensory vs. motor function)
Trigeminal, both sensory and motor
Function of CN V
Sensory signals from face (mouth, nose, eye, dura mater)
Motor fibers to the muscles of mastication
Name and briefly describe a condition causing dysfunction of CN V
Trigeminal neuralgia- hypersensitivity to pain in the areas innervated by CN V (ipsilateral face- eye, maxilla, mandible) caused by neurovascular or other compression or demyelination of CN V.
Herpes zoster opthalmicus- shingles in the opthalmic branch of trigeminal nerve
What is CN VI (name, sensory vs motor function)
Abducens, motor
Function of CN VI
motor- innervates lateral rectus of the eye
Dysfunction of CN VI causes?
Inability to ABDduct eye
Name all 12 cranial nerves
OOOTTAFVGVAH
olfactory, optic, oculomotor, trochlea, trigeminal, abducens, facial, vestibulocochlear, glossopharyngeal, vagus, accessory, hypoglossal
What is myasthenia gravis?
A chronic autoimmune disease affecting the neuromuscular junction characterized by weakness of voluntary muscles
Describe the epidemiology of myasthenia gravis
2 peaks- women in 20-30s, men in 60-60s.
Risk factors: frequently manifests for first time in pregnancy, exposure to anesthetic agents, thymic hyperplasia/ tumor, other autoimmune disorders
Time course of myasthenia gravis
insidious onset, relapse and remissions with gradual progression of disease.
What muscles are usually affected first in myasthenia graviS?
mouth, eyes, face, mouth, throat, neck
Classic triad: ptosis, diplopia, dysphagia
Describe patho of myasthenia gravis
Chronic autoimmune disorder: antibody mediated attack on acetylcholine receptors (the nicotinic receptor) at the post synaptic membrane of the neuromuscular junction. Decreased in these receptors= diminished transmission of nerve impulses across neuromuscular junction.
type 2 hypersensitivity reaction
T-cell mediated
Symptoms of myasthenia gravis
Classic triad: ptosis, diplopia, dysphagia
-difficulty chewing, drooling, slurred speech, easily fatigable, symptoms more pronounced with fatigue or in the evening
-normal sensory perception, pupillary response, coordination
-eye movement dysfunction, cannot sustain arm raise, change in voice when counting to 100
What is myasthenic crisis
Life threatening, risk of respiratory arrest, triggered when resp muscles weakened to the point of needing a ventilatory. Often triggered by infection, fever, adverse reaction to med.
Treatment myasthenia gravis
Cholinesterase inhibitors (stop breakdown of Ach, therefore increasing concentration in neuromuscular junction) *can result in cholinergic crisis that mimics myasthenic crisis, but problem is too much Ach instead of not enough (diarrhea, cramping, bradycardia, pupils constrict, increased salivation, risk for resp arrest)
What NT is involved in myasthenia gravis
Acetylcholine (the receptors (nicotinic receptors) in post synaptic side of the neuromuscular junction are destroyed :(
What is restless leg syndrome?
Neuro disorder characterized by unpleasant sensation in legs accompanied by urge to move legs, esp at bedtime
Risk factors restless leg
DM, ESRD, anemia, iron deficiency anemia, MS, PD, pregnancy, venous insufficiency
Time course restless leg
Worse at evening/ night time/ with rest, preventing sleep
Patho restless leg
Cause unknown- believed to involve genetic component, dysfunctional dopaminergic transmission, and low brain iron stores
Signs and symptoms restless leg syndrome
-Occur when the limbs are at rest and are relieved by movement
-Symptoms may extend to arms and trunk
-Commonly bilateral and symmetrical, but can be unilateral on occasion
-Sensation described as burning, nagging, aching, painful, itching bones, electric current, creepy crawl
Diagnosis of restless leg syndrome
does NOT require a sleep study
All of the following required: urge to move the legs, usually accompanied/ caused by unpleasant sensation in legs, symptoms begin or worsen during periods of rest of inactivity, symptoms are partially/ totally relived by movt, symptoms wose during evening/ night, symptoms cannot be due to another medical condition (i.e., arthritis)
positive supportive features: response to dopamine therapy
Treatment restless leg syndrome
Non pharm (sleep hygiene, hot baths, exercise moderately- yoga helps, massage, dc meds that can contribute (antidepressants, antiemetics, antihistamines, antipsychotics), avoid sleep deprivation
pharm: replace iron if deficient, dopaminergic agents, benzos, opioids, anticonvulsants, alpha 2 agonists
Describe the course and innervation of the median nerve
Arises from lateral and medial cords of brachial plexus, enters arm at axilla, travels with brachial artery down shaft of humerus into the cubital fossa, travels on ventral surface of forearm, passes through wrist through carpal tunnel (under the transverse carpal ligament) to hand.
Innervates all the muscles of the forearm anterior compartment (wrist and finger flexors, forearm pronators), ventral surface of thumb, 1st/ 2nd digit, half of 3rd digit
Most common cause of median nerve injury
carpal tunnel syndrome
What is carpal tunnel syndrome?
Median nerve become compressed in the carap tunnel (Osseo fascial tunnel composed of carpal bones and flexor retinaculum (fascia) due to swelling of tendons in the tunnel. Often caused by repetitive movements related to wrist flexion/ extension, holding wrist in awkward position, or strong gripping of objects
Signs and symptoms of carpal tunnel syndrome
- Tingling and numbness of the thumb, index, middle and ring fingers.
- Can also cause pain in the wrist with numbness/tingling
- Typically, the patient wakes at night with burning or aching pain and with numbness and tingling and shakes the hand to obtain relief and restore sensation.
- Long term compression leads to thenar muscle atrophy and weakness of the thumb and index fingers (can lead to hand of benediction- inability to flex middle and index finger)
Treatment of carpal tunnel
splinting, treat any underlying disorders contributing to inflammation, corticosteroid injection, surgical decompression
Describe two tests to support diagnosis of carpal tunnel
Tinel’s sign: lightly tapping on the ventral wrist over the median nerve elicits sensation of tingling/ pins and needles in the distribution of the nerve. Sensitivity 25-75%; specificity 70-90%.
Phalen’ maneuver: bring arms to shoulder level, bring back of hands together in midline, hold wrist in forced flexion for 30-60 seconds. Positive if tingling and numbness over median nerve distribution. Sensitivity 51-91%, specificity 33-88%
What is the most common compression neuropathy?
Carpal tunnel syndrome (followed by cubital- compression of ulnar nerve)
Describe the course and innervation of the radial nerve
Originates from brachial plexus, runs down radial groove of humerus to radial side of elbow, passes through supinator muscle, runs down middle of posterior forearm to dorsal thumb, 1st and 2nd digit.
Innervates extensors of the forearm, wrist, fingers, and thumb
What kind of injuries is the radial nerve susceptible to?
Entrapment can occur due to overuse injuries (most common pronation/ supination of wrist/ forearm)
Vulnerable to humeral mid shaft fracture
Can also sustain injury from improperly fitted crutches, shoulder dislocations, arm compression injuries
Can lead to wrist drop
Describe the course and innervation of the ulnar nerve
Down arm, passes posterior to medial epicondyle of humerus, travels along medial aspect of forearm, passes through the cubital tunnel at the wrist beneath the ulnar collateral ligament to the 4th/ 5th digit
Innervates flexors carpi ulnaris and most of intrinsic hand muscles. Sensation for 4th and 5th digits.
When you hit your funny bone, what nerve do you injure?
Ulnar
What is cubital tunnel syndrome
Compression/ traction of the ulnar nerve as it passes beneath the ulnar collateral ligament and between the two heads of the flexor carpi ulnaris muscle.
Where is the cubital tunnel?
Posterior aspect of elbow. Fibro-osseous tunnel.
Causes of cubital tunnel syndrome?
Leaning on the elbow, prolonged and excessive elbow flexion
Signs and symptoms of cubital tunnel
- Numbness and tingling along the ring and little fingers, and ulnar aspect of the hand
- Can present as elbow pain
- Long term compression causes weakness of intrinsic muscle of the hand and flexors of the ring and little finger
- Chronic compression leads to ulnar hand claw due to muscle imbalances (see picture below). An ulnar claw hand is metacarpophalangeal joint extension and interphalangeal joint flexion of the small and ring fingers caused by an imbalance between intrinsic and extrinsic hand muscles
What cranial nerve is CV VII?
Facial
What is cranial nerve VIII
Vestibulocochlear
What is cranial nerve IX
Glossopharangeal
Function of CV VII (facial)
Motor and sensory
- Facial expressions
- Supplies motor fibres to Lacrimal (tears) and salivary glands
- Taste (carries sensory fibres from taste buds of anterior part of tongue
Fx of CN VII (vestibulocochlear)
Sensory only
- Transmits sense of equilibrium (vestibular branch)
- Transmits sense of hearing (cochlear branch)
Fx of CN VIII (glossopharangeal)
Motor and sensory
- Motor fibres serve pharynx and salivary glands (gag and swallow reflex)
- Carries signals from pharynx, posterior tongue (taste) and pressure receptors of carotid artery
Cranial nerve VII (facial) dysfunction leads to what condition?
Bell’s Palsy
What is bell’s palsy? Unilateral or bilateral?
Unilateral facial nerve palsy (weakness or paralysis)
What causes Bell’s Palsy?
Exact etiology unknown, likely caused by inflammation of CNVII causing compression (CNVII travels through narrow canals in temporal bone and exits via the stylomastoid foramen).
May be due to reactivation of HSV in CNVII, or due to an autoimmune response.
Inflammation/ compression of CNVII leads to ischemia and degeneration, resulting in impaired signalling and transmission of motor impulses. Ipsilateral weakness or facial paralysis will result (along with loss of sensation in anterior tongue)
T/F With Bell’s Palsy, you will still see forehead wrinkling
False - this is impaired (unlike in stroke)
Risk factors for bell’s palsy
-Previous herpes simplex or herpes zoster infection, recent infection, diabetes, pregnancy (especially 3rd trimester), family history of Bell’s Palsy, hypertension, and hypothyroidism
Where do the Upper Motor Neurons arise?
Arise in the cerebral cortex
CN VII: where does it originate. How many branches does it contain?
CNVII originates in the Pons and runs through a narrow foramen of the temporal bone, out the stylomastoid foramen, through the parotid, and divides into 5 branches in the face (temporal, zygomatic, buccal, marginal mandibular, cervical)
Is onset of bell’s palsy slow or fast? How long does it take to resolve?
-Acute onset, progressing over hours to days
-Recovery in 3-4 weeks; may take up to 6 months (faster recovery occurs in mild/ moderate cases)
-Complete recovery in 80% of cases; without treatment, 70% of patients with complete and 94% with incomplete paralysis recover facial function in 6 months
What are the two tracts that upper motor neurons travel? Outline the path the signals travel on both tracts
Corticospinal – transports signals from cerebral cortex to lower motor neurons
Corticobulbar – transports signals from cerebral cortex to synapse with cranial nerve motor nuclei in the pons and medulla
S&S of bell’s palsy. Is it painful?
- Impaired forehead wrinkling
- Inability to close eye of affected side, drooping of eyelid
- Mouth drooping to affected side/ inability to smile
- Flattened nasolabial fold
- Can be associated with involuntary movements (synkinesis)
-Facial paresthesia
-Drooling
-Decreased tearing or abnormal lacrimation with eating
-Hypersensitivity to sound (hyperacusis)
-Ear pain
-Vesicular rash in ear (suggestive of Herpes Zoster cause and potential Ramsay-Hunt syndrome)
-Pain associated with facial palsy
-Change in sensation of taste (anterior tongue)
Is CT routine for bell’s palsy? WHen might we want one?
CT or MRI only if atypical presentation or physical findings suggestive of central lesion (affecting other cranial nerves, associated with limb weakness or ataxia), progressing paralysis, or lack of resolution
Meds used for bell’s palsy
Prednisone
Antivirals if severe
Eye drops
Acetaminophen
The corticospinal and corticobulbar tracts are the pyramidal tracts. What is the main function of the pyramidal system?
Allow for voluntary movements
In both types of pyramidal tracts some neurons decussate (crossover) to the contralateral side, while others stay ipsilateral. What percentage decussate in corticospinal and corticobulbar tracts?
Corticospinal:
Approximately 90% of neurons decussate (crossover) to contralateral side – known as lateral corticospinal tract in the white matter of the spinal cord
Approximately 10% of neurons stay ipsilateral and make up the anterior corticospinal tract
Corticobulbar:
50% of neurons synapse with lower motor neurons on ipsilateral side
50% decussate and synapse with lower motor neurons on the contralateral side
Where do lower motor neurons originate?
In the ventral horn grey matter of the spinal cord
What do lower motor neurons do?
Transport signals from the upper motor neuron to effector muscle to perform a movement
Use acetylcholine as their neurotransmitter
What is the neurotransmitter used by lower motor neurons?
Acetylcholine – binds with nicotinic cholinergic receptors on skeletal muscles resulting in muscle contraction
An upper motor neuron lesion can occur where? What are some possible causes?
result of damage to descending motor pathway at cortical, brainstem, or spinal cord levels
neoplasm, trauma, inflammation, cerebral palsy, MS, CVA, Parkinson’s
What muscle tone occurs with UMN leisons?
Muscle overactivity, Hypertonia/spasticity
In spinal shock- flaccid paralysis occurs for transient period followed by increased muscle tone particularly in antigravity muscles.